Surgical Instrument With Telescoping Attachment

ABSTRACT

A surgical instrument for the dissection of bone and other tissue includes a spindle, a dissection tool and an coupler disposed between the spindle and the dissection tool. The coupler includes a tool collet and an attachment locking mechanism operable to permit tool collet operation and telescoping movement of an attachment tube with respect to the dissection tool. A method is also provided for convenient coupling of the dissection tool and adjustment of the attachment tube length.

FIELD OF THE INVENTION

The present invention generally relates to surgical instruments for usein the dissection of bone and other tissue. More particularly, thepresent invention relates to a telescoping attachment for a surgicalinstrument.

BACKGROUND OF THE INVENTION

In various surgical procedures, it is necessary to dissect bone or othertissue. Many conventional surgical instruments used for the dissectionof bone or other tissue employ pneumatic or electrical motors to rotatea cutting element. In their most basic form, such surgical instrumentscomprise a motor portion having a rotary shaft, a dissection tool havinga cutting or abrading element that is moved by the rotating shaft of themotor, and a coupling arrangement for connecting the dissection tool toa spindle or collet of the rotary shaft. The spindle or collet of therotary shaft is usually housed within a base that is attached to themotor.

Because it is frequently necessary to replace the dissection tool, it isalso known in the art to use a quick release coupling to secure thedissection tool to the surgical instrument. An example of such a quickrelease coupling is shown and described in commonly assigned U.S. Pat.No. 5,505,737 entitled “Quick Release Coupling For A Dissecting Tool”incorporated herein by reference. The coupling device shown in U.S. Pat.No. 5,505,737 includes a spindle attachment which is secured to aspindle of a surgical instrument. The spindle attachment has a shaftengagement portion for engaging a shaft of the dissection tool. Theshaft engagement portion of the spindle attachment is provided withapertures that terminate within a central bore of the engagement portionthrough which the shaft of the dissection tool extends.

Powered surgical dissection instruments often utilize dissection toolshaving small shaft diameters in relation to their length. Such shaftsmay bend or flail in use if not adequately supported. This occurrencemay be heightened when such shafts are used with motors that aredesigned to reach speeds in excess of 72,000 rpm. Tool makers haveprovided attachments or tubes that engages the motor portion and receivea portion of the dissection tool shaft. Typically, such an attachmentwill include one or more bearing that support the dissection tool shaftat it extends from the tool collet. Attachments may be provided withmany configurations varying by length, diameter and function. Whiletelescoping attachments have been utilized which provide the capabilityof varying the distance the distal tip of the tube extends from themotor housing, the installation and adjustment of such devices remainscumbersome.

While known surgical tools include adjustable components, a need existsin the pertinent art for an improved surgical tool which permitstelescoping of the attachment relative to the motor.

SUMMARY OF THE INVENTION

In one particular embodiment, the surgical instrument includes a couplerfor telescopingly engaging an attachment tube to a surgical motor. In apreferred, but not required, aspect of the illustrated embodiment, thecoupling assembly may be manually manipulated to permit tool colletlocking and attachment tube adjustment without removal from the motor.

Additional advantages and features of the present invention will becomeapparent from the following description and appended claims, taken inconjunction with the accompanying drawings.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiments of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is an illustration of a surgical dissection tool according to thepresent invention used in a human patient.

FIG. 2A is a partially exploded perspective view of an embodiment of asurgical dissection tool according to the present invention.

FIG. 2B is a partially exploded perspective view of the embodiment ofFIG. 2A.

FIG. 2C is a partially exploded perspective view of the embodiment ofFIG. 2A.

FIG. 2D is an assembled perspective view of the embodiment of FIG. 2A.

FIG. 3 is an exploded perspective view of an embodiment of a telescopingattachment assembly according to the present invention.

FIGS. 4A and 4B are partial cross-sectional side views of the embodimentof FIG. 3 in an assembled and locked position.

FIGS. 5A and 5B are partial cross-sectional side views of the embodimentof FIG. 3 in an assembled and partially unlocked position.

FIGS. 6A and 6B are partial cross-sectional side views of the embodimentof FIG. 3 in an assembled and unlocked position.

FIG. 7 is an exploded perspective view of an embodiment of a telescopingattachment assembly according to the present invention.

FIGS. 8A and 8B are partial cross-sectional side views of the embodimentof FIG. 7 in an assembled and locked position.

FIGS. 9A and 9B are partial cross-sectional side views of the embodimentof FIG. 7 in an assembled and partially unlocked locked position.

FIGS. 10A and 10B are partial cross-sectional side views of theembodiment of FIG. 7 in an assembled and unlocked position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring now to FIG. 1, there is shown a human patient A undergoing aneurological operation. As is common practice, access to the brain orother neurological structures often requires delicate dissection of boneand other tissues B to gain access. By way of example, dissection toolassembly 10 in accordance with one aspect of the present invention isshown being utilized to dissect a portion of patient A's bone and othertissue B adjacent to the surgical access site.

Referring now to FIGS. 2A through 2D, a dissection tool assembly 10 forthe dissection of bone or other tissue is illustrated. A pneumatic motor20 is illustrated having a collet assembly 22 disposed on its distalend. Collet assembly 22 will not be described in great detail in thepresent application as it is more fully disclosed in a prior filedapplication U.S. Ser. No. 10/200,683 filed Jul. 22, 2002, entitled“Surgical Instrument with Rotary Cutting Member and Quick ReleaseCoupling Arrangement” incorporated by reference herein in its entirety.Collet assembly 22 includes a proximal movable portion 24 and a distalfixed portion 26. A shaft receiving aperture 28 is provided on thedistal end to slidably receive a rotary shaft. The dissection toolassembly 10 further includes an attachment base coupling assembly 30adapted to be received about collet assembly 22 and having an attachmentaperture 34 at its distal length. An attachment tube 40 is providedhaving a proximal portion 42 with grooves 44 extending along a portionthereof. The distal end of attachment tube 40 includes a tool receivingaperture 48. The coupling assembly 30 and attachment tube 40 may becombined to form a telescoping attachment assembly 12. An exemplaryillustration of a dissection tool 50 is also shown. Dissection tool 50includes an elongated shaft 52 and a tissue dissection head 54.

Referring now to FIG. 3, there is shown an exploded perspective view ofthe components of telescoping attachment assembly 12 according to oneembodiment of the present invention. Telescoping attachment assembly 12includes coupling assembly 30 and attachment 40. Dissection tool 50 isillustrated for purposes of completeness; however, it is not a requiredcomponent of telescoping attachment assembly 12 but is shown for use incooperation with the telescoping attachment assembly. Attachmentassembly 30 includes a body 110 having an outer surface and defining anaxially disposed internal passage 31 (FIG. 4A) extending substantiallythe length of body 110. Tool coupling assembly 120 is disposed withininternal passage 31. Tool coupling assembly 120 includes a split ring112, a bearing 114, a retaining ring 116, a bearing 118 disposed aboutthe proximal portion of a rotor shaft 121. Rotor shaft 121 includes acircumferential shoulder 124 and a proximal gripping end 122. A spring140 is disposed adjacent shoulder 124 and a locking sleeve 142 iscircumferentially disposed about gripping end 122 and held in positionby pen 144.

The distal end of coupling assembly 30 comprises attachment lockingassembly 160. Attachment locking assembly includes distal portion 36,tension ring 150 having apertures 151 disposed therein, split ring 152,spring 154, collar 156 having apertures 157 and locking ball 158disposed therein. Balls 166 are disposed within apertures 151 in theirassembled condition and similarly extend through apertures 164 disposedin body 110. Body 110 further defines collet fingers 163 at its distalextreme. A helical groove 162 is provided to receive locking balls 158.Helical groove 162 further includes shallow detents at either end of itslength. It will be understood that these shallow detents provide aprovisional locking of the locking balls when they reach this position,thereby maintaining the assembly in the select position. This may alsoprovide the user with tactile feedback as the balls fall into thedetents.

Attachment tube 40 comprises proximal portion 42 having a plurality ofaxially aligned grooves 44 disposed on the exterior surface. A proximalbearing assembly 45 is shown having a number of bearings, rings and atension spring illustrated there between. Bearing 51 is disposedproximally of proximal bearing assembly 45. Attachment tube 40 alsoincludes a distal bearing assembly 47. Proximal bearing assembly 45 anddistal bearing assembly 47 are fixably disposed within tube 46 and arepreferably adapted to support a rotating shaft. Proximal portion 42 isfixably attached to the exterior of tube 46 and retains bearing 51 inposition.

Referring now to FIGS. 4A through 6B, the details of tool couplingassembly 120 and attachment of locking assembly 160 will be more fullydescribed. Cross-sectional view of FIGS. 4A and 4B show telescopingattachment assembly 12 in the fully locked position. Dissection tool 50is locked within tool coupling assembly 120 and attachment tube 40 islocked within attachment locking assembly 160. As shown more fully inFIG. 4B, proximal portion 42 of attachment tube 40 extends withininternal chamber 34 of coupling assembly 30. Ball 166 is disposed withingroove 44 and is retained in this position by tension ring 150. Distalportion 36 has been rotated to the locked position moving balls 158within helical groove 162 to axially displace distal portion 36 in theproximal direction. As distal portion 36 moves in the proximaldirection, an internal tapered surface 37 engages an external taperedsurface 35 of collet fingers 163. The engagement between internaltapered surface 37 and external tapered surface 35 and the correspondingsurface on collet finger 165 urges the attachment locking assembly 160to constrict the diameter of attachment aperture 34 and therebylockingly engage proximal portion 42 of attachment tube 40. In thisposition, axially displacement of attachment tube 40 with respect tocoupling assembly 30 is inhibited.

Referring now specifically to FIGS. 5A and 5B, telescoping attachmentassembly 12 is shown with the attachment locking assembly 160 in anunlocked position and with tool coupling assembly 120 in a lockedposition. Distal portion 36 has been rotated with respect to motor 20 tourge balls 158 within helical groove 162. Movement of the balls 158within helical groove 162 urges distal portion 36 to be axiallydisplaced in a distal direction with respect to motor 20. Such distaldisplacement along the axis causes internal tapered surface 37 to bedisengaged from external tapered surface 35 such that attachmentaperture 34 effectively expands in diameter. In this state, attachmenttube 40 may be slidably displaced within attachment aperture 34. Groove44 is formed on proximal portion 42 such that it does not extend to theextreme proximal end and thereby creates a proximal shoulder 44a. Theengagement of ball 166 in groove 44 may thereby provide a tactilefeedback to the user when ball 166 is initially engaged in groove 44.With distal movement of the attachment tube 40 engaged in the lockingassembly 160, resistance upon engagement of ball 166 against shoulder 44a provides tactile feedback to the user that attachment tube 40 is aboutto be disengaged from coupling assembly 30. Further distal movement ofattachment tube 40 causes ball 166 to overcome the compressive force oftension ring 150 such that the attachment may be completely removed fromaperture 34.

Referring now to FIGS. 3, 5B and 6B, there are shown details of the toolcoupling assembly 120. Tool coupling assembly includes a locking sleeve142 disposed about gripping end 122. Locking sleeve 142 includes aninternal bore with a relief area 210, a projection 212, a further reliefarea 214 and a further projection 216. Gripping end 122 includes firstgripping finger 130 and a second complementary gripping finger 132. Thegripping fingers include a first ridge 220, a relief 222 and a secondridge 224, defined on their outer surface as shown in FIG. 5B. Theinternal surface of gripping finger 130 includes a projection 131 and adriving surface 134. In a similar manner, gripping finger 132 includes aprojection 133 and a driving surface 136. It will be understood thatthese driving surfaces and projections are substantially complementaryto corresponding features of recesses 58 and 60 and driving surfaces 62and 64 of dissection tool 50. As shown in FIG. 4B, the internal surfacesof the tool coupling assembly 120 substantially correspond to and matewith the external features of the dual driving pattern 56 to therebyretain the tool and effectively provide rotary force thereto. Lockingsleeve 142 is retained on gripping end 122 by means of pin 144 passingthrough a portion of the locking sleeve and extending through a slot 137defined between gripping finger 130 and gripping finger 132.

Tool coupling assembly 120 has a normally locked position such as thatshown in FIG. 4B and a second unlocked position shown in FIG. 6B. In thelocked position at FIG. 4B, projection 212 is in substantial axiallyalignment with ridge 220 and projection 216 is in substantial axiallyalignment with ridge 224 thereby urging gripping fingers 130 and 132into the locked position. In the second unlocked position illustrated inFIG. 6B, projection 212 is in substantial axially alignment with relief222 and projection 216 is disposed proximally of ridge 216. In a similarfashion, relief area 210 is disposed adjacent ridge 220 and relief area214 is disposed adjacent ridge 224. In this position, gripping fingers130 and 132 may move to their release position such that dissection tool50 may be removed from tool coupling assembly 120. It will beappreciated that spring 140 acts on locking sleeve 142 to urge thelocking sleeve into the first locked position. As shown in FIG. 6B,attachment proximal portion 42 is moved to the extreme proximal portionof attachment aperture 34 bringing bearing 51 into contact with lockingsleeve 142 whereby further proximal movement of attachment tube 40causes the locking sleeve to move into the second unlocked positionshown in FIG. 6B. Bearing 51 is provided as the contact surface betweenattachment tube 40 and locking sleeve 142 in the event that power wouldbe applied to rotor shaft 121. It will be understood that bearing 151may rotate with locking sleeve 142 to thereby isolate rotary force frombeing transmitted to attachment tube 40. As attachment tube 40 is moveddistally, spring 144 urges locking sleeve 142 into the first lockedposition shown in FIG. 4B.

Dissection assembly tool 10 may be assembled in the following manner,although the present invention is not limited to a specific sequence ofassembly. As shown at FIGS. 2A-2D, coupling assembly 30 may be slidablyadvanced over collet assembly 22 of motor 20. As described in the priorfiled application entitled “Surgical Instrument with Rotary CuttingMember and Quick Release Coupling Arrangement”, U.S. Ser. No. 10/200,683filed Jul. 22, 2002, axial rotation of coupling assembly 30 about motor20 causes rotational movement of movable portion 24 thereby actuating aninternal collet locking mechanism of motor 20 to rotationally mate withdrive pattern 126 of rotor shaft 121 (see FIG. 3). In a preferredaspect, rotation of coupling assembly 30 about motor 20 also locks thecoupling assembly to the motor. In the illustrated embodiment, theamount of rotation necessary to move from an unlocked position to alocked position is approximately 90 degrees. As best seen in FIG. 4A,coupling assembly 30 includes a pair of internal flats 33 disposedwithin internal chamber 31. It will be appreciated that as the couplingassembly 30 is slidably advanced with respect to motor 20, flats 33 willengage corresponding flats on collet assembly 22 to properly orient thetwo components. Moreover, upon rotation of coupling assembly 30 aboutmotor 20, flats 33 will drive movable portion 24 to operate the internaltool locking mechanism as well as being positioned behind fixed portion26 such that the coupling assembly is fixably engaged with motor 20.

Attachment tube 40 may be axially advanced within attachment aperture34. Grooves 44 may be positioned within attachment aperture 34 such thatretaining balls 166 (FIG. 4B) provisionally retain the attachment tube40 within coupling assembly 30. In the provisional retention state (FIG.5B), attachment tube 40 may be axially displaced within coupler 30. Withthe attachment joined to the coupler, dissection tool 50 may then beinserted through tool aperture 48 until the driving pattern 56 isdisposed adjacent the tool coupling assembly 120 of the couplingassembly 30. Attachment tube 40 may be then be moved along itslongitudinal axis distally toward motor 20 to thereby open the toolcoupling assembly 120 and the driving pattern 56 may then be advancedinto a locking position. Distal movement of attachment tube 40 away frommotor 20 results in dissection tool 50 being coupled to couplingassembly 30. Attachment tube 40 may then be moved with respect tocoupling assembly 30 to vary the distance between distal bearing 47 anddissection head 54. Once the desired displacement has been obtained,distal portion 36 may be rotated approximately 90 degrees in thedirection of arrow 38 with respect to motor 20 to thereby lock theposition of attachment tube 40 with respect to coupling assembly 30.

Disassembly of the dissection tool assembly 10 may be performed insubstantially the inverse order of operations described above toassemble the tool. More specifically, distal portion 36 may be rotatedin an opposite direction with respect to motor 20 thereby permit axialmovement of attachment tube 40 with respect to coupling assembly 30.Attachment tube 40 may then be moved proximally to engage the toolcoupling assembly 120 and move it to an unlocked position. Dissectiontool 50 may then be withdrawn from the tool coupling assembly 120 andfrom attachment tube 40. Thereafter, attachment tube 40 may be removedfrom coupling assembly 30 or a new dissection tool may be insertedthrough the attachment into locking engagement with coupling assembly30. It will be appreciated that coupling assembly 30 may be quickly andeasily removed from motor 20 by rotation in the opposite direction ofarrow 32 to move movable portion 24 to its unlocked position. This maybe accomplished with dissection tool 50 and attachment tube 40 fullyengaged in the distal end of coupling assembly 30.

Referring now to FIG. 7, there is shown an exploded perspective view ofthe components of an attachment assembly 300 according to anotherpreferred embodiment of the present invention. Telescoping attachmentassembly 300 includes attachment base 330 and attachment tube 340.Dissection tool 350 is shown for the purpose of illustration. Attachmentbase 330 includes an attachment locking assembly 378 and a tool lockingassembly 360 with a rotor shaft having gripping fingers 362. A spring368 is disposed about the gripping fingers 362 along with a portion oflocking sleeve 364. Locking sleeve 364 further includes an extension 366and an external shoulder 370. As previously described above, attachmenttube 340 includes several bearing assemblies adapted to rotationallysupport dissection tool 350. Proximal portion 343 includes a pluralityof axially aligned grooves 344 adapted for mating with projections ofthe attachment base 330.

Referring now to FIGS. 8A and 8B, telescoping attachment assembly 300 isshown with the tool locking assembly 360 and the attachment lockingassembly 378 in the locked position suitable for active operation to usethe dissection tool 350 to remove bone or other tissue. As shown ingreater detail in FIG. 8B, locking sleeve 364 is moved distally suchthat internal projections of the sleeve are in substantial alignmentwith projection on the exterior of gripping fingers 366 to urge thecollet to close on driving end 352 of dissection tool 350. Theattachment tube proximal portion 343 is positioned within the attachmentbase 330 such that grooves 344 may be engaged by inwardly extendingballs as previously described with respect to the embodiment of FIG. 3.The structure and operation of the attachment locking mechanism 378 issubstantially identical to that described with respect to the embodimentof FIG. 3 and will not be further described herein.

Locking sleeve 364 includes a distally extending extension 366 having aninternal bore with a diameter substantially matching the externaldiameter of tool 350 such that is provides support to the tool shaftduring operation. It will be understood that locking sleeve 364 andextension 366 will turn with tool 350 during operation. Extension 366extends within bearing 380 which is provided to isolate the rotation ofextension 366 from attachment tube 340.

The telescoping attachment assembly 300 is shown in the attachment tubeunlocked position and dissection tool locked position in FIGS. 9A and9B. Locking sleeve 364 remains in the locked position to urge grippingfingers 362 to lockingly engage tool 350. Attachment tube 340 is free tomove axially along the length of grooves 344. Bearing 380 is spaced fromexternal shoulder 370 and extension 366 extends through bearing 380 andinto sleeve 384. In this configuration, the distance between the distalend of attachment tube 340 and the attachment base 330 may be adjustedto the desired spacing.

Referring now to FIGS. 10A and 10B, the telescoping attachment assembly300 is shown with the attachment locking assembly 378 and the toollocking assembly 360 both in the unlock position. Attachment tube 340has been moved proximally along the longitudinal axis toward attachmentbase 330 until bearing 380 abuts external shoulder 370 on locking sleeve364. Further proximal movement of attachment tube 340 urges lockingsleeve 364 to move to the unlock position shown in FIG. 10B therebyallowing gripping fingers 366 to move to an unlock position. Tool driveend 352 may then be removed from the tool collet. Extension 366 is sizedto be received within bearing 380, sleeve 384 and spring 368. In theillustrated embodiment extension 366 does not contact bearing 382. Itwill be understood that distal movement of attachment tube 340 away fromattachment base 330 will allow the spring biased locking sleeve 364 tomove to the locked position.

The above description has been directed to a coupling assembly 30 thatis detachable from motor 20, however; it is contemplated and herebydisclosed that coupler 30 may be integrated with motor 20 in asubstantially integral unit. Still further, attachment tube 40 anddissection tool 50 have been shown as substantially straight components.It will be appreciated and is hereby disclosed that attachment tube 40may be curved to accommodate various applications. It being understoodthat dissection tool 50 may have sufficient flexibility to conform tothe curvature of the attachment along its length.

The above-described preferred embodiments of the present invention maybe assembled and adjusted by manual manipulation of the outer surfacesof the components. It will be understood that in this preferredconfiguration, it is advantageous for the user such that additionalinstrumentation, tools or intricate movements are not required toaccommodate the coupling and adjustment of the various components.

The above description of embodiments according to the invention ismerely exemplary in nature and, thus, variations that do not depart fromthe gist of the invention are intended to be within the scope of theinvention. Such variations are not to be regarded as a departure fromthe spirit and scope of the invention.

1-41. (canceled)
 42. A surgical instrument, comprising: a couplingassembly removably engaged with a motor assembly, the coupling assemblycomprising an axial bore extending from a proximal portion of thecoupling assembly to a distal portion of the coupling assembly along alongitudinal axis and comprising an attachment locking assembly adjacentthe distal portion; a tool-coupling assembly positioned at leastpartially within the axial bore of the coupling assembly; an attachmenttube removably engaged with the attachment locking assembly of thecoupling assembly and positioned at least partially within the axialbore of the coupling assembly, wherein in an unlocked state theattachment tube is movable with respect to the coupling assembly alongthe longitudinal axis, and wherein in a locked state the attachment tubeis fixed with respect to the coupling assembly; and a working toolcomprising a shaft with a distal working portion and a proximal couplingportion, the working tool extending through the attachment tube and theaxial bore of the coupling assembly such that the proximal portion ofthe working tool is removably engaged with the tool-coupling assembly.43. The surgical instrument of claim 42, wherein the coupling assemblyincludes a proximal housing portion and a distal housing portion, andwherein rotation of the proximal housing portion about the longitudinalaxis selectively locks the coupling assembly to the motor assembly. 44.The surgical instrument of claim 43, wherein rotation of the proximalhousing portion of approximately 90° about the longitudinal axisselectively locks the coupling assembly to the motor assembly.
 45. Thesurgical instrument of claim 43, wherein rotation of the distal housingportion about the longitudinal axis selectively locks the attachmenttube to the coupling assembly.
 46. The surgical instrument of claim 45,wherein rotation of the distal housing portion of approximately 90°about the longitudinal axis selectively locks the attachment tube to thecoupling assembly.
 47. The surgical instrument of claim 42, wherein theattachment tube is movable along the longitudinal axis with respect toboth the coupling assembly and the working tool when the proximalportion of the working tool is secured to the tool-coupling assembly.48. The surgical instrument of claim 42, further comprising a firstbearing assembly positioned within the attachment tube for supportingthe shaft of the working tool.
 49. The surgical instrument of claim 48,further comprising a second bearing assembly positioned within theattachment tube for supporting the shaft of the working tool, whereinthe first bearing assembly is positioned adjacent a proximal portion ofthe attachment tube and the second bearing assembly is positionedadjacent a distal portion of the attachment tube.
 50. The surgicalinstrument of claim 42, wherein at least a portion of the couplingassembly is movable along the longitudinal axis to selectively lock thecoupling assembly to the motor assembly.
 51. The surgical instrument ofclaim 42, wherein at least a portion of the coupling assembly is movablealong the longitudinal axis to selectively lock the attachment tube tothe coupling assembly.
 52. The surgical instrument of claim 42, whereinthe attachment tube is removably engaged with the attachment lockingassembly of the coupling assembly via a projection-and-detent retentionsystem.
 53. The surgical instrument of claim 52, wherein an outersurface of the attachment tube comprises a plurality of elongateddetents and wherein the attachment locking assembly includes at leastone projection for mating with one or more of the plurality of elongateddetents to form the projection-and-detent retention system.
 54. Thesurgical instrument of claim 53, wherein in the unlocked state the atleast one projection is slidable within the one or more of the pluralityof elongated detents to permit movement of the attachment tube along thelongitudinal axis with respect to the coupling assembly.
 55. Thesurgical instrument of claim 53, wherein in the locked state the atleast one projection is fixed within the one or more of the plurality ofelongated detents to prevent movement of the attachment tube along thelongitudinal axis with respect to the coupling assembly
 56. The surgicalinstrument of claim 42, wherein the motor assembly includes a tool chuckand the coupling assembly includes a work shaft, the work shaftremovably engaged to the tool chuck.
 57. A method of assembling asurgical dissection instrument, comprising: providing a motor assemblywith a first tool chuck; providing a coupling assembly with a work shaftand a second tool chuck; providing an attachment tube; providing adissection tool having a distal working portion and a proximal couplingportion; securing the coupling assembly to the motor assembly byengaging the work shaft with the first tool chuck; inserting theattachment tube into an axial bore of the coupling assembly to movablycouple the attachment tube to the coupling assembly; inserting theproximal portion of the dissection tool through the attachment and intothe second tool chuck; and locking the proximal portion of thedissection tool in the second tool chuck.
 58. The method of claim 57,further comprising translating the attachment tube along the dissectiontool after locking the proximal portion of the dissection tool in thesecond tool chuck to adjust the amount of the working portion of thedissection tool extending distally from the attachment tube; and fixedlysecuring the attachment tube relative to the coupling assembly anddissection tool.
 59. The method of claim 58, wherein fixedly securingthe attachment tube relative to the coupling assembly and the dissectiontool comprises engaging the attachment tube with an attachment lockingassembly of the coupling assembly.
 60. The method of claim 59, whereinfixedly securing the attachment tube relative to the coupling assemblyand the dissection tool comprises rotating a portion of the attachmentlocking assembly about the attachment tube.
 61. The method of claim 57,further comprising moving the attachment tube with respect to thecoupling assembly to unlock the proximal portion of the dissection toolfrom the second tool chuck and removing the dissection tool from theattachment.